Rotating seal assembly

ABSTRACT

A seal assembly for use between relatively rotatable inner and outer members. The seal assembly rotates relative to both the inner and outer members at a velocity intermediate the velocities of the inner and outer members.

United States Patent [72] Inventor Leslie A.Woodson FQREIGN PATENTS aBach, Calif. 512,372 9/1939 Great Britain 277/83 1 1 p 858393 759,23310/1956 Great Britain 277 165 1 1 Filed q I6, 1969 767,784 2/1957 GreatBritain 277/165 :alented Sept-w 5 78311 7: & C 1,166,648 6/1958 France277/165 ssignee am an o.

unmade, Cam. OTHER REFEREN'CES Huffman, Sl1pper Seals: O-nngs wlthTeflon" for low wear; The Journal ofTeflon Vol. 5 No. 4 May 1964 page 7re- [54] ROTATING SEAL ASSEMBLY lied upon.

14 Claims, 3 Drawing rm Primary Examiner-Robert 1. Smith [52] 0.5.277/165, 0 eySmyth, Roston & P t

' 277/83 [51] Int. Cl F16j15/54 [50] Fieldol Search 277M6 1, I65, 81, 81R, 83, 84

Afii: A seal assembly for use between relatively [56] Idem Cltedrotatable inner and outer members. The seal assembly rotates I UNITEDSTATES PATENTS relative to both the inner and outer members at avelocity in- 2,789,847 4/1957 Jackson 277/84 termediate the velocitiesof the inner and outer members.

PATEIHEU SEP 7127: 3503603 INI/ENTOR {W I LESLIE A. woooso/v ATTOEIVEY-S ROTATING EIEAIL ASSEMBLY BACKGROUND OF THE INVENTION In atypical seal installation it is desirable to seal between a rotatableshaft and an outer member surrounding the shaft. A seal assembly whichmay be in the form of an O-ringis positioned in a seal groove in themember and when the shaft rotates, the seal and the outer member remainstationary with the shaft rubbing against the seal assembly.

One persistent problem is that the seal assembly wears quite rapidly.Specifically, an elastomeric seal ring such as the conventional O-ringwears very rapidly if placed in rubbing contact between relativelymovable surfaces. To reduce wear on the elastomeric ring it has beenproposed to use a slipper seal. The slipper seal is placed between theO-ring and the rotatable shaft and the O-ring is, therefore, isolatedfrom rubbing contact with the shaft. The slipper seal is usuallyconstructed of a plastic material such as polytetrafluoroethylene whichis more wear resistant than the elastomeric material of the O-ring.

Notwithstanding the use of slipper seals, the wear problem still existsbecause the slipper seals are, themselves, subject to wear.Specifically, it has been found that slipper seal wear is very rapidwhen shaft velocity, as measured in surface feet per unit of time pastthe slipper seal exceeds a predetermined limit. For example, a velocityof 500 surface feet per minute is the maximum velocity which apolytetrafluoroethylene slipper seal can tolerate without experiencingextremely rapid wear. The result is that the shaft speed must be heldbelow a specified limit, or if shaft speed is increased beyondacceptable limits, the wear of a slipper seal progresses much morerapidly.

SUMMARY OF THE INVENTION The present invention substantially increasesseal life and/or permits substantial increase in shaft rotationalvelocity without increasing seal wear. This is accomplished by causingthe seal assembly to rotate relative to both the shaft member and theouter member at a velocity intermediate the velocities of the members.With this construction, the relative velocity between the seal assemblyand the members is less than it would be if the seal assembly was fixedto one of the members. By reducing the relative velocity, the wear onthe seal is correspondingly reduced. In addition, shaft speed can beincreased beyond the limits imposed by prior art seal assemblies.

For maximum wear life, the velocity of the seal assembly relative to theouter member as measured in surface feet per minute should be aboutequal to the velocity of the seal assembly relative to the shaft asmeasured in surface feet per minute. This causes the seal assembly towear evenly on the inner and outer circumferential surfaces thereof tothereby maximize seal life. Of course, the seal assembly velocity may bevaried with the amount of wear distribution depending upon the-velocityof the seal assembly relative to the shaft and outer member.

The seal assembly of this invention preferably includes a slipper sealwhich engages both the shaft and the outer member. The slipper seal maybe constructed of a low coefficient of friction plastic material such aspolytetrafluoroethylene. The slipper seal is caused to rotate bycontrolling the surface finish on the surfaces of the shaft and theouter member which engage the slipper seal. Thus, seal as semblyrotation is controlled by controlling the frictional forces acting onthe seal assembly.

The slipper seal is preferably loaded into sealing engagement with thewalls of the seal groove. This is preferably accomplished by a resilientelement such as an elastomeric sealing ring. The slipper seal shouldisolate the elastomeric sealing ring from rubbing contact with the shaftor outer member.

In one preferred form of the invention, two seal units are provided inthe seal groove with each of the seal units being held in axially spacedrelationship by a retainer element. Each of the seal units preferablyincludes a slipper seal and one or BRIEF DESCRIPTION OF THE DRAWINGSFIG. I is a fragmentary sectional view taken on an axial plane andillustrating a first form of seal assembly constructed in accordancewith the teachings of this invention.

FIG. 7. is a sectional view taken generally along line 22 of FIG. ll.

FIG. 3 is a fragmentary sectional view similar to FIG. I illustrating asecond form of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing and inparticular to FIG. 1 thereof, reference numeral lll designates -a sealassembly constructed in accordance with the teachings of this invention.The seal as sembly II is adaptedfor use between a rotatable shaft 13 andan outer member I5 which, in the embodiment illustrated, surrounds theshaft I3. The seal II is effective to prevent fluid under pressureacting in the direction of the arrow P (FIG. ll) from passing throughthe seal assembly.

The shaft III may be of conventional construction and be suitablymounted for rotation relative to the outer member 15. Ordinarily, theouter member ll5 will be stationary; however, the seal assembly II canbe utilized with either or both of the shaft l3 and the outer member l5being rotatable. Similarly, the seal assembly II can be utilizedregardless of the direction of rotation of the shaft l3 and/or the outermember IS.

The shaft 13 has a cylindrical outer surface 17 and the member l5 has aninner cylindrical surface 19 which confronts the surface 17. The outermember l5 also has a pair of axially spaced radial walls Zll and 23interconnected by a circumferential wall 25 which cooperate to define aseal groove in which the seal assembly Ill is positioned. If desired,the seal groove could be formed in the shaft 13 in lieu of the outermember 15.

The seal assembly ll includes a resilient ring 27 and a slipper seal 25.The resilient ring 27 and the slipper seal 29 are continuous sealingelements which completely circumscribe the shaft E as clearly shown inFIG. In the embodiment illustrated, the resilient ring 27 is in the formof an elastomeric O-ring and the slipper seal 29 is generally U- orchannel shaped in axial cross section with the U opening toward theradial wall 2E. The slipper seal 29 is preferably constructed of asomewhat deformable plastic material having good wear qualities such aspolytetrafluoroethylene.

As shown in FIG. l, the slipper seal 29 includes a pair of legs Fill and33 integrally interconnected by a radially extending web 35 all of whichcooperate to define the U-shaped slipper seal 2%. In the position shownin FIG. l the inner surface of the legs 3i and 33 converge as theyextend toward the opening of the U to thereby retain the resilient ring2.7 within the slipper seal 2.9. The resilient ring 2'7 is squeezedbetween the legs 31 and 33 and engages the web Elli. The web 35 has anouter surface 357 which engages the radial wall 23 and the legs 31 and33 have outer surfaces 39 and ll, respectively, which engage thecircumferential wall 25 and the outer surface l7.

Prior to its insertion into the seal groove, the outer surfaces of thelegs 3i and 33 of theslipper seal 29 diverge slightly and the innersurfaces of the legs are substantially parallel in axial cross'section.In the relaxed condition the resilient ring 27 is substantially circularin axial cross section, although other cross-sectional configurationscould be used. When the seal assembly fl is in the position shown FIG.I, the legs El and 31 are deflected slightly toward each other with theresult that the surfaces 39 and 41 are caused to engage, with somepressure, the radial wall 25 and the outer surface 17, respectively. Inaddition, the cross section of the resilient ring 27 is compressed sothat the resilient ring further urges the surfaces 39 and 41 into tightsealing engagement with the radial vall 25 and the outer surface 17,respectively.

The seal assembly 11 can be dynamically loaded by the fluid underpressure which travels between the surfaces 17 and 19 to act on the leftend of the seal assembly 11. This causes the surfaces 39 and 41 to moretightly engage the radial wall 25 and the surface 17, respectively. Thesurface 39 and 41 form radially thin annular gaps with the radial wall25 and the surface 17 as shown in FIG. 1 at regions adjacent the righthand end of the seal assembly 11.

A feature of this invention is that the seal assembly 11 rotatesrelative to the shaft 13 and the outer member 15 at a speed intermediatethe speeds of the shaft and the outer member. This desirable result isaccomplished, in this embodiment of the invention, by controlling thesurface finish on the radial wall 23, the circumferential wall 25 andthe outer surface 17. By so doing, the force of friction acting betweenthe seal assembly 11 and the shaft 13 and between the seal assembly 11and the outer member 15 can be controlled. By controlling the force offriction acting on the seal assembly 11, the movement of the sealassembly 11 can also be controlled. The particular surface finishselected will, therefore, depend upon various conditions such as thematerials from which the shaft 13, the outer member 15 and the slipperseal 29 are constructed and also the force with which the slipper sealis urged against the surface 17 and the walls 23 and 25. By way ofillustration, with a polytetrafluoroethylene slipper seal, an 8 to 16microinch finish has been found satisfactory.

Because of construction tolerances and variations in ressure to whichthe seal assembly 11 will be subjected, laboratory accuracy as to thespeed of rotation of the seal assembly 11 should not be anticipated. Insome instances, the seal assembly 11 may rotate intermittently. In anyevent, for optimum results the seal assembly 11 should rotate at such aspeed that the wear on the surfaces 39 and 411 are substantially equal.Theoretically this means that the number of surface feet per minute ofthe member 15 which passes the surface 39 should equal the number ofsurface feet per minute of the surface 17 which passes the surface 41.Because of the variation in diameters of the wall 25 and the surface 17,for optimum results, the seal assembly 11 should rotate at slightly lessthan one-half the rotational speed of the shaft (assuming that the shaft13 rotates and the outer member 15 is stationary). A close approximationof the optimum conditions is obtained with the seal assembly rotating atone-half shaft speed.

FIG. 3 shows a ringlike seal assembly 51 which is similar to the sealassembly 1 1 in that it rotates relative to a shaft 53 and an outermember 55. The shaft 53 may be identical to the shaft 13 except theformer has a passage 57 extending therethrough. In the embodimentillustrated, the shaft 57 has a radially extending portion which opensat an outer cylindrical surface 59 of the shaft and an axially extendingportion which may open at some other surface region of the shaft.

The outer member 55 surrounds the shaft 53 and has axially spaced radialwalls 61 and 63 interconnected by a circumferential wall 65 all of whichcooperate to define an annular seal groove. In the embodiment shown inFIG. 3, the radial wall 63 is defined by a removable ring 67 which isheld in position by a retaining ring 69 which is suitably retainedwithin a groove 71 of the outer member 55. The outer member 55 has apassage 73 which opens at the circumferential wall 65.

The seal assembly 51 includes seal units 75 and 77 which are maintainedin axially spaced relationship by a retainer 79. As the seal units 75and 77 are identical, only the seal unit 77 is described in detailherein.

The seal unit 77 includes an outer resilient ring $1, an inner resilientring 83 and an annular slipper seal 85. Each of the rings 81 and 113 maybe elastomeric sealing rings which are identical to the resilient ring27 (P16. 1). The slipper seal 85 includes an inner leg 87 and an outerleg 89 integrally interconnected by a web 91. The legs 87 and 89 havecircumferential surfaces 93 and 95, respectively, and the web 91 has anouter surface 97. The slipper seal 35 may be constructed of the samematerial as the slipper seal 29.

The retainer 79 is preferably an integral tubular element which extendscompletely around the shaft 53. The retainer 79 includes a pair ofretaining sections 99 and 101 located at opposite ends of the retainerand separated by a web 103. The retaining sections 99 and 101 areidentical and only the retaining section 1111 is described in detail.The retaining section 101 includes an axial flange 105, an inner radialflange 107 and an outer radial flange 109. The flange 105 radiallyseparates the resilient ring 81 and 83 and the radial flanges 107 and109 retain the resilient rings 83 and 81, respectively, against axialmovement to the left as viewed in FIG. 3. Thus, the retaining section101 cooperates with the slipper seal to substantially completely encloseboth of the resilient rings 81 and 33. The web 103 has one or moreapertures 111 extending generally radially therethrough to therebyprovide communication between the passages 57 and 73.

One feature of the construction shown in FIG. 3 is that a fluid can bepassed from the exterior of the outer member 55 through the sealassembly 51 and the passage 57 of the shaft 53 to another desiredlocation. If this fluid is under pressure, it can be utilized todynamically load the resilient rings 81 and 83 against the slipper seal85. in any event, the resilient rings 81 and 83 are radially compressedso that the surfaces 93 and are urged into sealing engagement withsurface 59 and the radial wall 65, respectively.

The seal assembly 51 is caused to rotate relative to the shaft 53 andthe outer member 55 at a velocity intermediate the velocities of theshaft 53 and the outer member. As in the construction shown in FIG. 1,this is accomplished by controlling the surface finish of the walls 61,63 and 65 and of the surface 59. The parameters useful in selectingsurface finish discussed hereinabove with reference to FIG. 1 areequally applicable to the embodiment of FIG. 3. Thus, the embodiment ofFIG. 3 possesses the capabilities of the embodiments of FIG. 1, and inaddition provides for the transfer of fluid in either direction throughthe passage 57, the aperture 111, and the passage 73. Of course, theseal units 75 and 77 and the retainer 79 all rotate relative to theshaft 53 and the outer member 55.

Although exemplary embodiments of the invention have been shown anddescribed, many changes, modifications and substitutions may be made byone having ordinary skill in the art without necessarily departing fromthe spirit and scope of this invention.

lclaim:

1. A seal assembly for use between relatively rotatable inner and outermembers comprising:

a resilient element for circumscribing the inner member;

a slipper seal for circumscribing the inner member and en gageable withboth of said members, said slipper seal holding said resilient elementsubstantially out of contact with the inner and outer members; and

means forming a driving connection between said slipper seal and atleast one of said members to thereby cause said slipper seal and saidresilient element to rotate together relative to both of the members ata velocity intermediate the velocities of the members to thereby reducewear on the slipper seal.

2. A seal assembly as defined in claim 1 wherein said slipper seal isgenerally U-shaped and said resilient element is positioned between thelegs of the U-shaped slipper seal, said U- shaped slipper seal openinggenerally axially.

3. A seal assembly as defined in claim 1 wherein said resilient elementincludes an elastomeric seal ring and said slipper seal is constructedof a plastic material.

4 A seal assembly as defined in claim 1 wherein said means for causingincludes friction drive means between said slipper seal and saidmembers.

5. A seal assembly as defined in claim 11 wherein said means for causingincludes the surfaces of said slipper seal which engage the members, thecoefficients of friction of said surfaces being selected to cause saidmembers to drive said slipper seal at said intermediate velocity.

s. A seal assembly and associated structure comprising:

an inner member;

an outer member circumscribing said inner member, said members beingrelatively rotatable;

one of said members having first and second axially spaced,

radial walls and a circumferential wall cooperating with said radialwalls to define a circumferentially extending groove;

a seal assembly in said groove;

said seal assembly including first and second axially spaced elastomericseal ring means circumscribing the inner member and a retaining elementextending between said elastomeric seal rings means to maintain saidelastomeric seal ring means in axially spaced relationship; and

said seal assembly including first and second slipper seal means forsubstantially holding the first and second elastomeric seal ring means,respectively, out of contact with said members, said first and secondslipper sea] means engaging both of said members 7. A seal assembly andassociated structure as defined in claim 6 wherein the surface finish ofthe surfaces of said members which engage said slipper seal means arecontrolled so as to cause said seal assembly including said retainingelement to rotate relative to both of said members at a velocityintermediate the velocities of said members.

b. A seal assembly and associated structure as defined in claim 6wherein each of said elastomeric sealing ring means includes inner andouter elastomeric seal rings with said inner seal ring being positionedradially inwardly of said outer seal ring, said retaining elementincluding a separating portion separating the inner and outer sealrings.

9 A seal assembly and associated structure as defined in claim 6 whereinsaid retaining element and said first slipper seal means cooperate tosubstantially completely confine said first elastomeric seal ring means.

lltit. A seal assembly and associated structure as defined in claim 6including means for defining a passage through both of said members andsaid retaining element whereby material can flow through the sealassembly between said members, said passage extending through saidretaining element intermediate said first and second elastomeric sealring means.

11. A seal assembly and associated structure comprising:

an inner member;

an outer member circumscribing said inner member, said members beingrelatively rotatable;

one of said members having first and second axially spaced, radial wallsand a circumferential wall cooperating with said radial Walls to definea circumferentially extending groove;

a seal in said groove, said seal including a resilient element and aslipper element, each of said elements circumscrib ing the inner member;

said slipper element having circumferentially extending inner and outersurfaces engaging cooperating surfaces on the inner and outer members,respectively, said slipper element substantially isolating the resilientelements from contact with said members; and

the surface finish of said cooperating surfaces of said mern bers beingselected so as to cause said seal to rotate relative to both of saidmembers at a velocity intermediate the velocities of said members.

112. A seal assembly and associated structure as defined in claim llwherein the velocity of said seal is approximately one-half the relativevelocity between said members.

13. A sea] assembly defined in claim 1111 wherein said slipper elementincludes inner and outer leg portions defining said circumferentiallyextending inner and outer surfaces, respective ly, said resilientelement being at least partially between said leg portions and urging atleast one of said inner and outer surfaces into engagement with theassociated member, one of said cooperating surfaces being saidcircumferential wall.

M. A seal assembly as defined in claim 13 wherein said slipper elementis constructed of a plastic material and said resilient element isconstructed of elastomeric material, said leg portions being joined by agenerally radially extending Web which generally confronts one of saidradial walls.

1. A seal assembly for use between relatively rotatable inner and outermembers comprising: a resilient element for circumscribing the innermember; a slipper seal for circumscribing the inner member andengageable with both of said members, said slipper seal holding saidresilient element substantially out of contact with the inner and outermembers; and means forming a driving connection between said slipperseal and at least one of said members to thereby cause said slipper sealand said resilient element to rotate together relative to both of themembers at a velocity intermediate the velocities of the members tothereby reduce wear on the slipper seal.
 2. A seal assembly as definedin claim 1 wherein said slipper seal is generally U-shaped and saidresilient element is positioned between the legs of the U-shaped slipperseal, said U-shaped slipper seal opening generally axially.
 3. A sealassembly as defined in claim 1 wherein said resilient element includesan elastomeric seal ring and said slipper seal is constructed of aplastic material.
 4. A seal assembly as defined in claim 1 wherein saidmeans for causing includes friction drive means between said slipperseal and said members.
 5. A seal assembly as defined in claim 1 whereinsaid means for causing includes the surfaces of said slipper seal whichengage the members, the coefficients of friction of said surfaces beingselected to cause said members to drive said slipper seal at saidintermediate velocity.
 6. A seal assembly and associated structurecomprising: an inner member; an outer member circumscribing said innermember, said members being relatively rotatable; one of said membershaving first and second axially spaced, radial walls and acircumferential wall cooperating with said radial walls to define acircumferentially extending groove; a seal assembly in said groove; saidseal assembly including first and second axially spaced elastomeric sealring means circumscribing the inner member and a retaining elementextending between said elastomeric seal rings means to maintain saidelastomeric seal ring means in axially spaced relationship; and saidseal assembly including first and second slipper seal means forsubstantially holding the first and second elastomeric seal ring means,respectively, out of contact with said members, said first and secondslipper seal means engaging both of said members.
 7. A seal assembly andassociated structure as defined in claim 6 wherein the surface finish ofthe surfaces of said members which engage said slipper seal means arecontrolled so as to cause said seal assembly including said retainingelement to rotate relative to both of said members at a velocityintermediate the velocities of said members.
 8. A seal assembly andassociated structure as defined in claim 6 wherein each of saidelastomeric sealing ring means includes inner and outer elastomeric sealrings with said inner seal ring being positioned radially inwardly ofsaid outer seal ring, said retaining element including a separatingportion separating the inner and outer seal rings.
 9. A seal assemblyand associated structure as defined in claim 6 wherein said retainingelement and said first slipper seal means cooperate to substantiallycompletely confine said first elastomeric seal ring means.
 10. A sealassembly and associated structure as defined in claim 6 including meansfor defining a passage through both of said members and said retainingelement whereby material can flow through the seal assembly between saidmembers, said passage extending through said retaining elementintermediate said first and second elastomeric seal ring means.
 11. Aseal assembly and associated structure comprising: an inner member; anouter member circumscribing said inner member, said members beingrelatively rotatable; one of said members having first and secondaxially spaced, radial walls and a circumferential wall cooperating withsaid radial walls to define a circumferentially extending groove; a sealin said groove, said seal including a resilient element and a slipperelement, each of said elements circumscribing the inner member; saidslipper element having circumferentially extending inner and outersurfaces engaging cooperating surfaces on the inner and outer members,respectively, said slipper element substantially isolating the resilientelements from contact with said members; and the surface finish of saidcooperating surfaces of said members being selected so as to cause saidseal to rotate relative to both of said members at a velocityintermediate the velocities of said members.
 12. A seal assembly andassociated structure as defined in claim 11 wherein the velocity of saidseal is approximately one-half the relative velocity between saidmembers.
 13. A seal assembly defined in claim 11 wherein said slipperelement includes inner and outer leg portions defining saidcircumferentially extending inner and outer surfaces, respectively, saidresilient element being at least partially between said leg portions andurging at least one of said inner and outer surfaces into engagementwith the associated member, one of said cooperating surfaces being saidcircumferential wall.
 14. A seal assembly as defined in claim 13 whereinsaid slipper element is constructed of a plastic material and saidresilient element is constructed of elastomeric material, said legportions being joined by a generally radially extending web whichgenerally confronts one of said radial walls.